Back panel for flat panel display apparatus, flat panel display apparatus comprising the same, and method of manufacturing the back panel

ABSTRACT

A back panel for a flat panel display apparatus includes: a pixel electrode disposed on a substrate; a first gate electrode layer of a thin-film transistor (TFT) disposed on the substrate; a second gate electrode layer disposed on the first gate electrode layer and including a semiconductor material; a third gate electrode layer disposed on the second gate electrode layer and including a metal material; a first insulating layer disposed on the third gate electrode layer; an active layer disposed on the first insulating layer and including a transparent conductive oxide semiconductor; a second insulating layer disposed on the active layer; source and drain electrodes disposed connected to the active layer through the second insulating layer; and a third insulating layer covering the source and drain electrodes. The first gate electrode layer and the pixel electrode include a transparent conductive oxide.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No.10-2011-0050187, filed on May 26, 2011, which is hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Exemplary embodiments of the present invention relate to a back panelfor a flat panel display apparatus, a flat panel display apparatusincluding the same, and a method of manufacturing the back panel.

2. Discussion of the Background

Flat panel display apparatuses, including organic light-emitting displayapparatuses and liquid crystal display apparatuses, include active backpanels that include thin-film transistors (TFTs) and capacitors formedin each pixel, to realize high resolution displays.

In particular, oxide semiconductor TFTs are regarded as optimum devicesfor use in back panels of flat panel display apparatuses, because theyprovide excellent electrical characteristics and can be processed at alow temperature. However, the process for manufacturing back panels thatinclude the oxide semiconductor TFTs includes the use of a plurality ofmask processes, thereby increasing manufacturing costs.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a back panel thatcan be manufactured in a simple process and has a high display quality,a flat panel display apparatus including the back panel, and a method ofmanufacturing the back panel.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

Exemplary embodiments of the present invention provide a back panel fora flat panel display apparatus, the back panel including: a pixelelectrode that is formed on a substrate and includes a transparentconductive oxide; a gate electrode including a first gate electrodelayer of a thin-film transistor TFT that is formed on the same layer asthe pixel electrode and is formed of the same material as the pixelelectrode, a second gate electrode layer that is formed on the is firstgate electrode layer and includes a semiconductor material, and a thirdgate electrode layer that is formed on the second gate electrode layerand includes a metal material; a first insulating layer covering thethird gate electrode layer; an active layer that is formed on the firstinsulating layer and includes a transparent conductive oxide; a secondinsulating layer covering the active layer; source and drain electrodesthat are formed on the second insulating layer and are connected to theactive layer through the second insulating layer; and a third insulatinglayer covering the source and drain electrodes.

Exemplary embodiments of the present invention provide a flat paneldisplay apparatus including: a back panel for the flat panel displayapparatus described above; a facing electrode that faces the pixelelectrode; and a light-emitting layer formed between the pixel electrodeand the facing electrode.

Exemplary embodiments of the present invention provide a method ofmanufacturing a back panel of a flat panel display apparatus, the methodincluding: forming a first electrode material layer on a substrate, thefirst electrode material layer comprising a transparent conductivematerial layer, semiconductor material layer, and a metal layer;performing a first mask process on the first electrode material layer toform a pixel electrode and a gate electrode; forming a first insulatinglayer and a transparent conductive oxide layer, on the substrate;performing a second mask process on the transparent conductive oxidelayer to form an active layer on the gate electrode; forming a secondinsulating layer on the substrate; performing a third mask process toforming a contact hole through the second insulating layer and avia-hole through the first and second insulating layers to expose aportion of the pixel electrode; forming a second electrode materiallayer on the substrate; performing a fourth mask process on the secondelectrode material layer to form source and drain electrodes thatcontact the active layer through the first holes, and to form openingsin the first and second insulating layers that expose portions of thepixel electrode; forming a third insulating layer on the substrate; andperforming a fifth mask process to form an opening to expose the firstlayer of the pixel electrode.

A back panel according to aspects of the present invention, a flat paneldisplay apparatus including the back panel, and a method ofmanufacturing the back panel provide the following advantages.

First, the back panel can be manufactured using five mask processes.

Second, because a semiconductor layer as a protection layer is formed ona transparent pixel electrode, damage to the transparent pixel electrodeduring the manufacturing process can be prevented.

Third, the optical efficiency of a display apparatus can be increased,by forming the pixel electrode using a semi-transparent metal.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic cross-sectional view of an organic light-emittingdisplay apparatus, according to an exemplary embodiment of the presentinvention.

FIG. 2 is a schematic cross-sectional view of a product of a first maskprocess, according to an exemplary embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a product of a second maskprocess, according to an exemplary embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a product of a third maskprocess, apparatus according to an exemplary embodiment of the presentinvention.

FIG. 5 is a schematic cross-sectional view of a product of a fourth maskprocess, according to an exemplary embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a product of a wet etchingprocess in the fourth mask process, apparatus according to an exemplaryembodiment of the present invention.

FIG. 7 is a schematic cross-sectional view of a product of a dry etchingprocess in the fourth mask process, according to an exemplary embodimentof the present invention.

FIG. 8 is a schematic cross-sectional view of a product of a fifth maskprocess, according to an exemplary embodiment of the present invention;

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent.

FIG. 1 is a schematic cross-sectional view of an organic light-emittingdisplay apparatus 1, according to an exemplary embodiment of the presentinvention. FIGS. 2 through 8 are schematic cross-sectional views of amethod of manufacturing the organic light-emitting display apparatus 1of FIG. 1, according to an exemplary embodiment of the presentinvention.

Referring to FIG. 1, the organic light-emitting display apparatus 1includes a substrate 10 having a pixel region PXL including alight-emitting layer 19, a thin-film transistor region TFT including athin-film transistor, and a capacitor region CAP including a capacitor.In the pixel region PXL, a pixel electrode 111 that includes atransparent conductive material is formed on the substrate 10. The pixelelectrode 111 may include a transparent conductive material, such asindium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO),indium oxide (In₂O₃), indium gallium oxide (IGO), or aluminum zinc oxide(AZO), or any combination thereof.

The pixel electrode 111 may be formed as a multiple layer structure thatincludes a semi-transparent metal layer 111 b that includes silver (Ag).For example, as depicted in FIG. 1, the pixel electrode 111 may includea semi-transparent metal layer 111 b, and transparent layers 111 a and111 c that are formed on and under the semi-transparent metal layer 111b. The semi-transparent metal layer 111 b may include Ag, and thetransparent layers 111 a and 111 c may include a transparent conductivematerial, such as ITO. The semi-transparent metal layer 111 b functionsas a semi-transparent mirror and may form a resonance structure,together with a facing electrode 20. The resonance structure canincrease the optical extraction efficiency of the organic light-emittingdisplay apparatus 1.

A first protection layer 112 may be formed on an upper surface of thepixel electrode 111, for example, upper edges of the pixel electrode111. The first protection layer 112 is a protective film for preventingthe degradation of the pixel electrode 111 during a manufacturingprocess of the pixel electrode 111. In FIG. 1, the first protectionlayer 112 is disposed on upper edges of the pixel electrode 111.However, the present invention is not limited thereto. That is, thefirst protection layer 112 may be present only at an opening C2.

The first protection layer 112 may include a semiconductor material. Thesemiconductor material may be crystalline silicon or amorphous siliconthat is highly doped. The semiconductor material may be an oxide thatincludes zinc (Zn), gallium (Ga), hafnium (Hf), indium (In), or tin(Sn), or any combination thereof.

A metal layer 113 including a low resistance metal material may beformed on the first protection layer 112. The metal layer 113 mayinclude the same material used to form a third gate electrode 213described below. For convenience, the pixel electrode 111, the metallayer 113, and the first protection layer 112, may be collectivelyreferred to as a pixel electrode.

A first insulating layer 14 and a second insulating layer 16 aresequentially formed on edges of the pixel electrode 111. The pixelelectrode 111 is exposed through an opening C3 formed in the first andsecond insulating layers 14 and 16. A third insulating layer 18 isformed on the second insulating layer 16. An opening C4 that exposes aportion of the is pixel electrode 111 is formed in the third insulatinglayer 18.

The light-emitting layer 19 is formed on the exposed pixel electrode111. Light generated by the light-emitting layer 119 may be emittedtowards the substrate 10 and may pass through the transparent pixelelectrode 111.

The light-emitting layer 19 may be formed of a low molecular weightorganic material or a polymer organic material. If the light-emittinglayer 19 is formed of a low molecular weight organic material, a holetransport layer (HTL), a hole injection Layer (HIL), an electrontransport layer (ETL), and an electron injection layer (EIL) may bestacked around the light-emitting layer 19. The low molecular weightorganic material may be various materials including copperphthalocyanine (CuPc), N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine(NPB), or tris-8-hydroxyquinoline aluminum (Alq3). If the light-emittinglayer 19 is formed of a polymer organic material, a HTL may be includedbesides the light-emitting layer 119. The HTL may be formed ofpoly-(2,4)-ethylene-dihydroxy thiophene (PEDOT) or polyaniline (PANI).The organic material may be a poly-organic material, such aspolyphenylene vinylene (PPV), and polyfluorene.

The facing electrode 20 is formed on the light-emitting layer 19 as acommon electrode. In the organic light-emitting display apparatus 1, thepixel electrode 111 is used as an anode and the facing electrode 20 isused as a cathode. However, the present invention is not limitedthereto, and the polarities of the pixel electrode 111 and the facingelectrode 20 may be reversed.

The facing electrode 20 may be formed as a reflective electrode thatincludes a reflective material. The facing electrode 20 may include Al,Mg, Li, Ca, LiF/Ca, or LiF/Al, or any combination thereof. Lightgenerated by the light-emitting layer 19 may be reflected by the facingelectrode 20 towards the substrate 10. If the pixel electrode 111includes the semi-transparent metal layer 111 b, the semi-transparentmetal layer 111 b may function as a semi-transparent mirror, and mayform a resonance structure together with the facing electrode 20,thereby increasing the optical extraction efficiency of the organiclight-emitting display apparatus 1.

In the thin-film transistor TFT region, a first gate electrode layer211, a second gate electrode layer 212, and the third gate electrodelayer 213 are sequentially formed on the substrate 10. The first gateelectrode layer 211 is formed from the same layer of material as thepixel electrode 111. When the pixel electrode 111 is formed as amultiple layer structure, the first gate electrode layer 211 may also beformed as a multiple layer structure.

The second gate electrode layer 212 is formed from the same layer ofmaterial as the first protection layer 112. That is, the second gateelectrode layer 212 may include an oxide that includes crystallinesilicon or amorphous silicon that is highly doped with a dopant such as,Zn, Ga, Hf, In, and Sn.

The third gate electrode layer 213 may be formed from the same layer ofmaterial as the metal layer 113. Although not shown, the third gateelectrode layer 213 may be used as a gate wire.

An active layer 215 of the TFT may be formed on the first insulatinglayer 14, facing the third gate electrode layer 213. The active layer215 includes a conductive oxide semiconductor and may be transparent.The conductive oxide semiconductor may include Zn, Ga, Hf, In, and/orSn. For example, the conductive oxide semiconductor may include InGaZnO,ZnSnO, InZnO, InGaO, ZnO, TiO, and/or hafnium-indium-zinc oxide (HIZO).

As described above, the oxide semiconductor TFT provides excellentdevice characteristics and can be processed at a low temperature.Furthermore, because the oxide semiconductor TFT may have transparentcharacteristics in a visible light region and is flexible, the oxidesemiconductor TFT may be applied to a transparent display apparatus or aflexible display apparatus.

The second insulating layer 16 is formed so as to cover the active layer215. Source and drain electrodes 217 a and 217 b are formed on thesecond insulating layer 16 and are connected to the active layer 215,through openings C1 formed in the second insulating layer 16. In thepixel region PXL, the drain electrode 217 a is connected to the uppersurface of the pixel electrode 111 through an opening C2 formed in thefirst and second insulating layers 14 and 16.

The first protection layer 112 and the metal layer 113 may besequentially stacked on the pixel electrode 111 and disposed in theopening C2. The drain electrode 217 b may be connected to the pixelelectrode 111, by directly contacting the metal layer 113 through theopening C2.

In the capacitor region CAP, a first lower electrode layer 311, a secondlower electrode layer 312, and a third lower electrode layer 313 aresequentially formed on the substrate 10. The first lower electrode layer311 is formed from the same layer of material as the pixel electrode 111and the first gate electrode layer 211. The second lower electrode layer312 is formed from the same layer of material as the first protectionlayer 112 and the second gate electrode layer 212. The third lowerelectrode layer 313 is formed from the same layer of material as themetal layer 113 and the third gate electrode layer 213.

That is, the first, second, and third lower electrode layers 311, 312,and 313 are respectively formed by the same mask processes used to formthe pixel electrodes 111 and 112, the metal layer 113, and the first,second, and third electrode layers 211, 212, and 213. Therefore, themanufacturing processes are simplified.

The first and second insulating layers 14 and 16, which function asdielectric layers, are formed on the third lower electrode layer 313. Acapacitor upper electrode 317 is formed on the second insulating layer16. The capacitor upper electrode 317 is formed from the same layer ofmaterial as the source and drain electrodes 217 a and 217 b. Thecapacitor upper electrode 317 is formed during the same mask process asthe source and drain electrodes 217 a and 217 b. Thus, the manufacturingprocess may be simplified.

The third insulating layer 18 is formed so as to cover the source anddrain electrodes 217 a and 217 b and the capacitor upper electrode 317.As described above, an opening C4 that exposes the pixel electrode 111is formed in the third insulating layer 18.

Hereinafter, a method of manufacturing the organic light-emittingdisplay apparatus 1, according to an exemplary embodiment of the presentinvention, will now be described with reference to FIGS. 2 through 8.FIG. 2 is a schematic cross-sectional view of a product of a first maskprocess of the method of manufacturing the organic light-emittingdisplay apparatus 1, according to an exemplary embodiment of the presentinvention.

Referring to FIG. 2, the pixel electrode 111, the first protection layer112, and the metal layer 113 are formed in the pixel region PXL, thefirst gate electrode layer 211, the second gate electrode layer 212, andthe third gate electrode layer 213 are formed in the thin-filmtransistor region TFT, and the first lower electrode layer 311, thesecond lower electrode layer 312, and the third lower electrode layer313 are formed in the capacitor region CAP, using the same mask process.A buffer layer (not shown) that includes SiO₂ and/or SiN_(x) may furtherbe formed on the substrate, to planarize the substrate 10 and to blockpenetration of foreign elements into the substrate 10.

Although not depicted in detail, the structure of FIG. 2 is formed aftersequentially depositing a transparent conductive material, asemiconductor material, and a metal on the substrate 10. A photoresist(not shown) is coated on the on the resultant product. Then a first maskprocess is performed using the photoresist as a mask, to form thestructure of FIG. 2. The first mask process may be a photolithographyprocess. The first mask process may include a series of processes, suchas developing, etching, and stripping or ashing, after exposing thefirst mask (not shown) using an exposure apparatus (not shown).

As depicted in FIG. 1, when the pixel electrode 111 further includes thesemi-transparent metal layer 111 b, the semi-transparent layers 111 aand 111 c may further be included on and under the semi-transparentmetal layer 111 b. The first gate electrode layer 211 and the firstlower electrode layer 311 may also be formed as multiple layerstructures.

FIG. 3 is a schematic cross-sectional view of a product of a second maskprocess of the method of forming the organic light-emitting displayapparatus 1, according to an exemplary embodiment of the presentinvention. The first insulating layer 14 is formed on the structure ofFIG. 2. The active layer 215 is formed on the first insulating layer 14.The active layer 215 includes a transparent conductive oxide.

FIG. 4 is a schematic cross-sectional view of a product of a third maskprocess of the method of forming the organic light-emitting displayapparatus 1, according to an exemplary embodiment of the presentinvention. The second insulating layer 16 is formed on the product ofthe second mask process. Openings C1 are formed in the second insulatinglayer 16 to expose portions of the active layer 215. Openings C2 and C3that expose portions of the upper surface of the metal layer 113 areformed in the first and second insulating layers 14 and 16. At thispoint, the first protection layer 112 and the metal layer 113 remain onthe pixel electrode 111. Thus, the first protection layer 112 and themetal layer 113 protect the pixel electrode 111 during the formation ofthe openings C1, C2, and C3.

FIG. 5 is a schematic cross-sectional view of a product of a fourth maskprocess of the method of forming the organic light-emitting displayapparatus 1, according to an exemplary embodiment of the presentinvention. An electrode material layer 17 that covers the openings C1,C2, and C3 and includes a material for forming the source and drainelectrodes 217 a and 217 b is deposited on the product of the third maskprocess. A photoresist P is then formed thereon. A photolithographyprocess is performed using a fourth photomask M having a light-blockingportion M1 and a light-transmitting portion M2.

When the photoresist is a positive type photoresist, the portion of thelayer 17 corresponding to the light-transmitting portion M2 is removed.The source and drain electrodes 217 a and 217 b and the capacitor upperelectrode 317 are formed on a region corresponding to the light-blockingportion M1.

FIG. 6 is a schematic cross-sectional view of a product of a wet etchingprocess W/E of the fourth mask process, according to an exemplaryembodiment of the present invention. When portion of the layer 17corresponding to the light-transmitting portion M2 is removed, a portionof the metal layer 113 on the first protection layer 112 may also beremoved when the source and drain electrodes 217 a and 217 b are formed.In particular, portions of the metal layer 113 and the layer 17 may bereadily removed by a wet etching process. At this point, the firstprotection layer 112 is not removed during the wet etching process W/E.Thus, the pixel electrode 111 is protected.

FIG. 7 is a schematic cross-sectional view of a product of a dry etchingprocess in the fourth mask process, according to an exemplary embodimentof the present invention. A portion of the first protection layer 112 isremoved, for example, by a dry etching process D/E. When the pixelelectrode 111 includes a transparent conductive oxide, the pixelelectrode 111 may be damaged while the wet etching process W/E isperformed. However, because the first protection layer 112 is removedafter the wet etching process W/E is performed, the first protectionlayer 112 may protect the pixel electrode 111.

When the pixel electrode 111 is formed as a multiple layer structure,during the wet etching process W/E, the first protection layer 112prevents the semi-transparent metal layer 111 b from being damagedthrough pin holes formed in the semi-transparent metal layer 111 c.Accordingly, damage to the semi-transparent metal layer 111 b isprevented, thereby preventing a reduction of optical efficiency of adisplay apparatus.

FIG. 8 is a schematic cross-sectional view of a product of a fifth maskprocess of the method of forming the organic light-emitting displayapparatus 1, according to an exemplary embodiment of the presentinvention. The third insulating layer 18 is formed on the product of thefourth mask process. An opening C4 that exposes an upper surface of thepixel electrode 111 is formed by removing a portion of the thirdinsulating layer 18.

A back panel that includes a bottom gate type oxide semiconductor,according to an exemplary embodiment of the present invention, can bemanufactured by a total of five mask processes. Therefore, manufacturingcosts can be greatly reduced.

The present invention is described with reference to an organiclight-emitting display apparatus; however, the present invention is notlimited thereto. For example, the present invention may also be appliedto a liquid crystal display apparatus. Also, the present invention maybe applied to various other types of display apparatuses.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A back panel for a flat panel display apparatus,the back panel comprising: a pixel electrode disposed on a substrate andcomprising a transparent conductive oxide; a thin-film transistor (TFT)gate electrode comprising a first gate electrode layer disposed on thesame layer as the pixel electrode and comprising the same type ofmaterial as the pixel electrode, a second gate electrode layer disposedon the first gate electrode layer and comprising a semiconductormaterial, and a third gate electrode layer disposed on the second gateelectrode layer and comprising a metal; a first insulating layerdisposed on the third gate electrode layer; an active layer disposed onthe first insulating layer; a second insulating layer disposed on theactive layer; a first TFT electrode and a second TFT electrode disposedon the second insulating layer and connected to the active layer throughthe second insulating layer; and a third insulating layer disposed onthe first TFT electrode and the second TFT electrode, wherein the firstTFT electrode is electrically connected to the pixel electrode.
 2. Theback panel of claim 1, wherein the transparent conductive oxidecomprises at least one selected from the group consisting of indium tinoxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide(In₂O₃), indium gallium oxide (IGO), and aluminum zinc oxide (AZO). 3.The back panel of claim 1, wherein the pixel electrode further comprisesa semi-transparent metal layer disposed under the transparent conductiveoxide.
 4. The back panel of claim 3, wherein the semi-transparent metallayer comprises silver (Ag).
 5. The back panel of claim 3, wherein thepixel electrode further comprises a transparent conductive layerdisposed under the semi-transparent metal layer.
 6. The back panel ofclaim 1, wherein the active layer comprises a conductive oxidesemiconductor that comprises at least one element selected from thegroup consisting of zinc (Zn), gallium (Ga), hafnium (Hf), indium (In),and tin (Sn).
 7. The back panel of claim 1, wherein the second gateelectrode layer comprises a doped semiconductor material.
 8. The backpanel of claim 7, wherein the doped semiconductor material comprisessilicon.
 9. The back panel of claim 1, wherein the second gate electrodelayer comprises an oxide semiconductor material.
 10. The back panel ofclaim 1, wherein the oxide semiconductor material comprises at least oneselected from the group consisting of Zn, Ga, Hf, In, and Sn.
 11. Theback panel of claim 1, wherein the first TFT electrode is electricallyconnected to the pixel electrode through a first opening in the firstinsulating layer and the second insulating layer.
 12. The back panel ofclaim 11, further comprising: a protection layer comprising the sametype of material as the second gate electrode layer; and a metal layerdisposed on the protection layer and comprising the same type ofmaterial as the third gate electrode layer, wherein, the protectionlayer and the metal layer are disposed on an edge of the pixelelectrode, and the first TFT electrode directly contacts the metal layerthrough the first opening.
 13. The back panel of claim 1, furthercomprising a capacitor comprising: a first lower electrode layerdisposed on the same layer as the pixel electrode; a second lowerelectrode layer disposed on the first lower electrode layer; and a thirdlower electrode layer disposed on the second lower electrode layer. 14.The back panel of claim 13, wherein: the first lower electrode layercomprises the same type of material as the first gate electrode layer;the second lower electrode layer comprises the same type of material asthe second gate electrode layer; and the third lower electrode layercomprises the same type of material as the third gate electrode layer.15. The back panel of claim 13, wherein the capacitor further comprisesan upper electrode disposed on the second insulating layer.
 16. Adisplay apparatus comprising: a back panel of claim 1; a facingelectrode that faces the pixel electrode; and a light-emitting layerdisposed between the pixel electrode and the facing electrode.
 17. Thedisplay apparatus of claim 16, wherein the facing electrode is areflective electrode that reflects light generated by the light-emittinglayer.
 18. The display apparatus of claim 16, wherein the light-emittinglayer comprises an organic light-emitting layer.